Cannelured frangible projectile and method of canneluring a frangible projectile

ABSTRACT

A method of canneluring a frangible projectile includes the steps of rotating the projectile at a high speed, and cutting the cannelure into the projectile to form a frangible cannelured projectile. To ensure that the body is not damaged during cutting, the cutting tool has bevels on each side of a square, generally flat, cutting surface. A frangible cannelured projectile made by the foregoing method includes a groove having a generally flat base and beveled edges.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a frangible projectile, and in particular to afrangible projectile having a cannelure. The invention also relates to amethod of canneluring a frangible projectile.

2. Description of Related Art

The Cartridge Collector's Glossary-Illustrated, published byInternational Ammunition Association, 2001, and made available on theirwebsite, defines a “cannelure” as “the circumferential swaged, machinedor milled groove(s) around a bullet (for sealing; also often foridentification) to a cartridge case.” The cannelure is used, forexample, as a guide during crimping of a small arms cartridge to thebullet, and/or for retaining a lubricant. While bullets can be securedto cartridges without using cannelures, cannelures are preferred in manycases because they provide a more secure, accurate, and efficient way ofattaching the cartridge to the projectile.

A variety of conventional bullets or other projectiles includingcannelures are disclosed in U.S. Pat. Nos. 5,259,320; 5,275,108;5,105,514; 5,079,986; 4,811,666; 4,517,897; 4,336,756; 2,409,307;1,944,884; and 326,231.

While canneluring is well-known in the context of conventionalprojectiles, it has heretofore been impractical to provide cannelures infrangible projectiles, which are designed to break apart upon impact,rather than penetrating the target. Conventional machining or millingtechniques tend to fracture or weaken the projectile, which is typicallymade of a compressed powder rather than solid material.

Frangible projectiles are generally lighter than conventionalprojectiles, and are often used as practice rounds on firing ranges orin situations where non-lethal force is required. To achievedisintegration, frangible projectiles are conventionally made ofpowdered and compressed materials, rather than solid metal. Originallymade of lead powders, frangible projectiles have more recently been madeof less toxic materials such as compressed copper and tin powders.

Cannuluring of frangible projectiles is desirable for the same reasonsthat apply to other types of projectiles, including secure and simpleattachment of cartridge shells, identification, and lubrication.Nevertheless, there have only been a few attempts to provide canneluredprojectiles, and none has proven practical for mass-market civilianapplications. Examples of conventional frangible projectiles that lackcannelures are disclosed in U.S. Published Patent Application Nos.2003/0101891 and 2001/0050020 and U.S. Pat. No. 6,536,352.

An early attempt at canneluring a frangible projectile is disclosed inU.S. Pat. No. 2,105,528, which is specifically directed to a small armsprojectile for use in shooting galleries, including a “grease groove”corresponding to the cannelure of a conventional projectile. However,the method disclosed in this patent can only be used with lead powdermixtures, and is in any case unsuitable for use with modern frangibleprojectiles, since it involves hardening the projectile before formingthe cannelure by crimping or swaging.

Another “frangible” projectile with a cannelure is disclosed in U.S.Pat. No. 5,442,989. The projectile includes a penetrating rod andincendiary component, with the body of the projectile being arranged notonly to disintegrate upon contact, but to disintegrate into granulesthat are propelled outwardly “in every direction with great energy” inorder to increase the damage caused by the projectile prior topenetration. The cannelure is used to hold a rotator band or ring forengaging the rifling of a gun barrel, the groove being molded into thebody of the projectile prior to sintering. Again, the method disclosedin this patent is not suitable for application to frangible projectilesof the type intended for general use, because it requires hardening ofthe projectile after molding the groove into the body of the projectile.

There is consequently a long-felt need for a method that enablescannelures to be formed in frangible powdered metal type projectilesintended for general use.

SUMMARY OF THE INVENTION

It is accordingly an objective of the invention to provide a method ofcanneluring a frangible projectile.

It is a further objective of the invention to provide a method ofcanneluring a frangible projectile, without the need to harden theprojectile, and which is suitable for use with powdered metalcompositions, including lead-free compositions.

It is also an objective of the invention to provide a frangibleprojectile made of a compressed powdered material, and that includes acannelure.

These objectives are achieved by a method of making a projectileincluding the steps of rotating the projectile at a high speed, andcutting the cannelure into the projectile using a specially shapedcutting tool having a generally flat cutting surface and beveled edges.

A particular advantage of being able to cannelure a projectile that isfrangible is that the cannelure acts as a perforation, which causes theprojectile to break during attempts to remove the projectile from thecartridge into which it is crimped, thereby discouraging separation ofthe cartridge from the projectile.

The term “frangible projectile” as used herein refers to the property ofdisintegrating upon contact with a target, rather than penetrating thetarget. It is not intended to include projectiles, sometimes alsoreferred to as frangible, that are hardened or equipped with a solidmetal rod for penetration, but contain an explosive charge that causesdisintegration or fragmentation upon entry into the target.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a cannelured frangible projectile made by themethod of the invention.

FIG. 2 is a flowchart illustrating a method of canneluring a frangibleprojectile, according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in FIG. 1, a projectile made by the method of theinvention includes a frangible projectile body 1 having a cannelure 2and an otherwise conventional shape. Body 1 is made of a lead-freecompressed powder mixture such as copper powder and tin powder.

It will be appreciated by those skilled in the art that the material ofthe projectile may be entirely conventional, and that the invention isnot to be limited to a particular material, so long as the projectile isfrangible. For reasons of toxicity, lead-free compositions arepreferred, although the method of the invention could also be applied tolead-containing frangible projectiles, and to projectiles containingother materials or substances.

Due to the use of a special cutting tool, described below, whichprevents the body from being weakened or damaged during cannelureformation, the preferred projectile illustrated in FIG. 1 includes agenerally flat base 3 and beveled sides 4.

Dimensions of the groove for a typical small arms powered copper-tinprojectile or bullet, including but not limited to a .223 caliber bullet(0.223″ or 5.56 mm), are 0.002″ deep by 0.030″ wide at the base. Theangle of the bevel is 45 degrees so that the top of the groove has awidth of 0.050 inches. The axial position of the groove will depend onthe specific application, including the type of cartridge in which theprojectile is to be secure, while the width and depth of the groove, aswell as the angle of the bevel, may also be varied depending on thecaliber of the projectile, the application in which it is to be used,and the exact composition of the projectile material.

Although projectiles made by the method of the invention need notnecessarily have this property, the illustrated cannelure has thefurther advantage of acting as a perforation to cause the projectile tobreak during attempts to remove the projectile from the cartridge intowhich it is crimped, thereby discouraging separation of the cartridgefrom the projectile in order to ensure proper handling and use of thecartridge.

The first step of the method of the invention, as illustrated in FIG. 2,is to position, in a cutting machine, a projectile that has been made bycompressing a powdered material to form a frangible projectile body(step 100). The pre-cannelured projectile body itself is entirelyconventional and forms no part of the present invention.

The projectile is then rotated around its longitudinal or cylindricalaxis at a high speed (step 200). Finally, a properly dimensioned cuttingblade is applied to the body of the projectile in order to machine-cutthe groove or cannelure (step 300).

A conventional cutting tool will fracture the frangible projectile.Therefore, the cutting tool used in the preferred method has bevelededges and a square or rectangular cutting surface corresponding to theshape of the groove 2 illustrated in FIG. 1. In particular, the cuttingtool used in the method of the invention may have, by way of example andnot limitation, a width 0.050″ with 45 degree bevels on each lateraledge of the cutting surface. Each bevel is 0.010″×0.010″, and thecutting tool preferably has a square cutting surface having a width of0.030″. Although the invention is not limited to the illustrateddimensions, the width of the cut resulting from the above tool is0.050″+/−0.008″ and the depth of the cut is 0.0021″+/−0.010″. Asindicated above, the position of the cannelure on the projectile dependson the overall length of the loading specifications for the finishedcartridge.

Having thus described a preferred embodiment of the invention insufficient detail to enable those skilled in the art to make and use theinvention, it will nevertheless be appreciated that numerous variationsand modifications of the illustrated embodiment may be made withoutdeparting from the spirit of the invention, and it is intended that theinvention not be limited by the above description or accompanyingdrawings, but that it be defined solely in accordance with the appendedclaims.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. A frangible bullet having acannelure, comprising a body made of a compressed powdered metalmaterial that disintegrates upon contact with an object; and a cannelurecut into the compressed powered metal material, wherein the cannelureincludes beveled edges and a generally flat base.
 5. A frangible bulletas claimed in claim 4, wherein the beveled edges are at an approximately45 degree angle relatively to a flat base of the cannelure.
 6. Afrangible bullet as claimed in claim 4, wherein the compressed powderedmetal material comprises a lead-free powder material.
 7. A frangiblebullet as claimed in claim 6, wherein the compressed powdered metalmaterial comprises a copper tin powder mixture.
 8. A frangible bullet asclaimed in claim 4, wherein the bullet is a small arms bullet.
 9. Afrangible bullet as claimed in claim 8, wherein the bullet is a riflebullet and the cannelure is arranged to be crimped to a cartridge. 10.(canceled)